Method

• 1.
  For the cake, place the oranges in a medium saucepan and cover generously with water. Bring to the boil and boil for 1 hour, topping up water if necessary, until tender when pierced with a skewer. Drain.
• 2.
  When cool enough to handle, quarter oranges and discard seeds. Place in a blender and whiz for 1-2 minutes until a smooth puree. Set aside to cool.
• 3.
  Preheat oven to 160°C/140°C fan-forced.
• 4.
  Grease a 20cm x 30cm slice pan and line base and sides with baking paper.
• 5.
  Place eggs and sugar in a stand mixer fitted with the paddle attachment. Mix on high speed until light in colour. Add orange puree, almond meal and baking powder and mix until well combined.
• 6.
  Spoon into prepared pan and bake for 1 hour 5 minutes or until a skewer inserted in centre comes out clean. Cool in pan on a wire rack.
• 7.
  For the caramel, place the sugar in a small saucepan with 2 tbs water. Cook over low heat, stirring until sugar dissolves. Increase heat to high and cook, without stirring, until a deep golden colour.
• 8.
  Carefully and slowly add the orange juice (the mixture will bubble up). Stir until combined and smooth. Set aside to cool.
• 9.
  For the buttercream, place eggs and 1/2 tsp fine salt in a stand mixer fitted with the whisk attachment and whisk on high speed for 5 minutes until mixture forms ribbons when whisk is lifted.
• 10.
  Meanwhile, place sugar and 2 tbs water in a small saucepan. Cook over medium heat, stirring until sugar dissolves. Increase heat to high and cook until mixture reaches 114°C on a sugar thermometer.
• 11.
  With motor running on low, slowly add the hot syrup to the egg mixture, then increase speed to high and whisk until the bowl no longer feels warm to the touch. Add cubes of butter, one at a time, whisking until each is completely melted and incorporated before adding the next (if the mixture looks curdled, continue adding butter, then whisk at high speed until mixture comes together again).
• 12.
  Switch to paddle attachment and add the chocolate. Scrape down side of bowl and beat until well combined.
• 13.
  Turn cooled cake out onto a serving plate. Spoon buttercream into a piping bag fitted with a medium star nozzle, and pipe stars onto the cake. Drizzle with caramel and sprinkle with lemon zest.